1. Field of the Invention
The present invention relates to a streaming delivery system, in which a client who reproduces streaming data and a media server for distributing the streaming data are connected by at least one kind of network, and in which a cache server is located in the network between the client and the media server, and relates to a cache server apparatus and cache method for dispersing a load of the media server by caching the streaming data with the cache server and reducing congestion of the network between the client and the media server.
The network which delivers the streaming data includes, for example, the Internet, digital TV networks, satellite communication, and any other kinds of communication means, regardless of wired or wireless.
2. Description of the Related Art
In the streaming delivery system through the network, the streaming data delivered by the media server is precisely divided and delivered according to the communication rule. As the client receives the divided data, the client reproduces the data.
The cache server apparatus which is located between the client and the media server, caches the streaming data sent/received between the client and the media server, and delivers cached streaming data instead of the media server in response to a request for the same streaming data by another client.
In this way, it is avoidable that too many requests from clients gather at the media server, and it is possible to reduce a traffic load of the network.
The Japanese Unexamined Patent Publication No. 2001-69485 discloses a proxy server, which operates in the above way, for a video-on-demand system through the network.
The streaming data is not static data, so that, generally, it is necessary to send/receive a predetermined amount of data within a predetermined time. For example, the media data having a predetermined reproducing time such as video or sound is delivered from the media server with keeping real time, and the client reproduces the streaming data, as it receives the streaming data delivered from the media server.
An apparatus and a method for caching the streaming data, considering a characteristic of the streaming data, is disclosed in Japanese Unexamined Patent Publication No. 2000-293424. According to this invention, in case of caching the streaming data in response to the request from the client, if the request from the client is suspended, instead of the client, the cache server apparatus obtains data of a time period of the streaming data and stores in the cache.